Is the crack opened or closed in soft-matter pentagonal and decagonal quasicrystal

The hydrodynamic model for possible pentagonal and decagonal soft-matter quasicrystals is investigated, the effect of fluid which describes the difference of fracture theory between traditional structural material and the present novel material is considered. With this model, taking into account of equation of state, a complete hydrodynamics analysis is carried out. In the plane field of the soft-matter quasicrystals, the phonon, phason and fluid fields in time-spatial domain are quantitatively explored. A fluid stress intensity factor is suggested for the first time, whose physical action here leads to the closing of the crack surface, so is different from that of elastic (or phonon) stress intensity factor which leads to opening of the crack surface. The authors consider the cracking process of soft-matter quasicrystals is a process of competition between action of elastic stress and fluid stress to each other. In other words, the situation around the crack tip of the matter in stable or unstable lies in the competition results.